Problem with restart in free-boundary about spec HOT 6 CLOSED

Here is an example of input file (one has to remove the .txt extension) that illustrates what I mean.

l2freeboundaryexample_L0.sp.txt

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As identified by @SRHudson , the problem is that the angle constraint coefficient sweight , which is defined in preset.h, was proportional to tflux in each volume. However, in free-boundary and e.g. Lconstraint=0, the toroidal (and poloidal) flux in the outermost volume, namely the vacuum volume, is modified in order to ensure the constraint of the linking current(s). Thus, when force-balance is obtained, the restart .end file contains a converged geometry but the value of tflux (which is the one initially in the input) has not changed, so that when the code is run again with this new file as input, the part of the force-balance that corresponds to the angle constraints is not converged. For example, one gets initially:

newton : 6.03 : 0 0 ; |f|= 5.43747E-03 ; time= 5.87s ; log|BB|e=-16.44
newton : : ; ; log|II|o= -3.10

from spec.

One way to fix this, as proposed by @SRHudson, is to remove the dependency of sweight on tflux,

SALLOCATE( sweight, (1:Mvol), zero )
!sweight(1:Mvol) = upsilon * tflux(1:Mvol)**wpoloidal
do vvol = 1, Mvol ; sweight(vvol) = upsilon * (vvol*one/Nvol)**wpoloidal
enddo

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I created a branch called fixrestart and applied this change. I checked that the code compiles and runs, and that the restart problem has been indeed fixed.

An important caveat is that the angle constraint (and therefore the angle definition itself) is different than before, even if running the same case. That makes comparison with previous runs very hard: the physical solution should not change, but for example the harmonics Rmn,Zmn,etc. will be different.

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One alternative would be to keep the definition of sweight as before and write in the .end file the new values of tflux that have been calculated during the previous run.

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Problem solved via the branch fixrestart. Closing issue.

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